The present invention relates to a distributor board for compressed air monitoring systems, and more particularly, for electric cables under air pressure. The distributor board comprises a plurality of flow detectors disposed in a common distributor housing, with the flow detectors being connected both to a common compressed air line and to a cable to be supplied with compressed air, and with the detectors causing a signal to be emitted when a predetermined regulatable air flow is exceeded.
German Pat. Nos. 1,035,754 and 1,056,260 describe flow detectors in which the flow of compressed air to be monitored flows through a feed conduit towards a piston, which is displaceable in the feed conduit, and passes through lateral discharge openings provided in the conduit into a housing unit covered with an inspection glass, and from which it is discharged via a flow measuring glass. The flow measuring glass includes a float member and the level of the float floating on the air current in the flow measuring glass can be read from a scale and represents a measurement of the respective flow rate or quantity.
The piston disposed in the feed conduit is mounted in a position of equilibrium which is determined by the value of the air flow and by a spring force counteracting the latter. The piston is mounted in the region of the lateral discharge openings. Even minimal flow variations can cause the piston to change its position and this is used to activate a contact for producing a warning signal. The value of the flow required to produce such a triggering action can be adapted to suit different requirements.
Flow detectors of this type are used, for example, to monitor electric cables which are placed under air pressure to prevent the penetration of moisture. Any loss due to unavoidable sealing leaks in the cable must be compensated in order to maintain the pressure inside the cable. If the amount of air required to maintain this pressure, i.e., the flow to the cable, varies, this indicates that the cable is still subject to leakage or that it has been damaged. Flow detectors enable such a leak to be detected very rapidly.
At a cable distribution station, the flow detectors corresponding to the individual outgoing cables are generally grouped together on distributor panels which are mounted in a common frame, in which is located a compressed air line for each distributor panel, with compressed air supply lines for the individual flow detector branching from the common line. A stop valve which can be operated from the front side of the distributor panel to enable a defective cable to be disconnected from the compressed air supply is provided in the line leading to each flow detector. A flow quantity exceeding the tolerance limit is indicated by means of a warning light activated by means of the above-mentioned contact and the value of this flow quantity can be observed from the measuring glass.
On account of the sheet metal work involved, distribution panels of this nature are not only costly to produce because they give rise to high installation costs when the individual flow detectors are installed and connected up, but also require considerable space. This latter requirement can constitute a fairly substantial disadvantage if a large number of pressure gas cables are to be monitored.